Re: [softrock40] Sound Cards
----- Original Message -----
Subject: [softrock40] Sound Cards
>A 24 bit sound card won't buy you anything if you are just using it to decode audio in fldigi but there is a big difference if you
>are using it for i/q. Any doubters out there need to look at the comparisons here:
This thread started with the question whether 24 bit cards could improve the Softrock.
These links, those I can see, are all about noise floor. This is what I understand to be the advantage with 24 bits. Not actual
resolution so that the signal may be better analysed?
My tests seem to show that a Softrock needs to be modified, gain reduced, to make any use of lower noise 24 bit soundcards.
Others, yes, on the Mobo group have confirmed that reducing the gain does increase the dynamic range.
So I agree that if a Softrock is modified and gains carefully adjusted greater dynamic range is possible with 24 bits. Obviously it
is not easy to evaluate the effect of non-linearity on data decoding. My feeling is that over a narrow bandwidth it probably will
make little difference. In any case we might be talking about a reasonably good card used with a 16 bit driver.
Warren started all this and I think he is correct. Unless you modify a Softrock 24 bits will make little, if any, difference.
73 Alan G4ZFQ
(http://mobokits.stormwarning.org/node/6/610). While it is true that 24 bit cards do not deliver 24 bits nor does 16 give 16 bits.
You also need to look at how bad the linearity is on cheap cards.
> Or just google:
> EMU0202 vs EMU1212M vs FA66 192Ksps RX.doc
- Good point.
Thanks for the heads up.
73 - Bill KA8VIT
Date: Tue, 28 Oct 2014 13:49:44 -0700
Subject: Re: [softrock40] RE: Sound Cards
In deciding on a sound card, one thing to look into is the freq response. My $200 "pro audio recording" 24/96 sound card (FocusRite Scarlett 2i2) has very low input noise, but for SDR use the 96 kHz rate provides no wider window than 48 kHz b/c the 22 kHz anti-aliasing filter is used at 96 kHz, which is understandable if the intended purpose is for normal audio. The $29 SIIG 24/96 card that I reported had a high input noise level (actually for most situations with large outdoor antennas the band noise would still be higher than this card's noise) does allow a 96 kHz wide window, but there is nothing in the "specs" that tells you whether this is the case or not. I would be concerned that higher cost "audiophile" cards might have 22 kHz filter in place for all sampling rates unless I could confirm otherwise.__.